Vehicle suspension systems

ABSTRACT

The invention relates to a suspension system ( 10,12 ) for installation between a chassis ( 14,16 ) and dual axles ( 18,20 ) of a vehicle. The suspension system ( 10,12 ) includes an equaliser beam ( 22 ) pivotally linking the axles ( 18,20 ) together. A trailing arm support member ( 14 ) is pivotally attached to a hanger bracket ( 68 ) on chassis ( 14,16 ). A suspension saddle ( 58 ) is secured to trailing arm support ( 64 ) to provide pivotal support for equaliser beam ( 22 ) and air spring means ( 72 ) located between chassis ( 14,16 ) and trailing arm support member ( 64 ).

[0001] The invention relates to vehicle suspension systems for dual axlevehicles in which the axles are attached to equaliser beams or morecommonly known as walking beams, so that the vehicle load is transferredto the road surface either equally, or in proportion, to the position ofthe beam pivot to the beam centre.

[0002] Various vehicle suspensions have been developed for dual axlevehicles in which the axles are attached to walking beams with aspringing medium located between the beam pivot and the vehicle chassisto absorb shocks caused by uneven road conditions. Additionally amechanical connection system is used between the walking beam and thechassis to firstly transmit tractive effort and torque; secondly toabsorb braking effort and torque; and thirdly to constrain the lateralrelationship of the axles with the chassis. In the case where thespringing mechanism uses steel springs, the spring is usually amulti-leaf semi elliptical type or a taper leaf type, having an eye atthe forward end and a slipper surface at the rear end. The spring andits associated saddle then performs all or part all of the requiredfunctions of the mechanical connection system. In the case where thespringing mechanism uses rubber springs, or air springs, the mechanicalconnection systems are usually vertical drive pins and load cushionslocated in vertical aligned rubber bushings.

[0003] Air suspensions are generally recognised as having desirablefeatures including superior ride comfort for the driver; enhanced impactprotection for the vehicle and cargo; and reduced road impact andconsequent road wear. Air suspension with walking beams and verticaldrive pins have the benefits of previously mentioned desirable featuresreduced because the vertical drive pins and associated bushings tend torestrict vertical freedom of the suspension.

[0004] It is an object of the invention to provide a suspension systemwhich combines the advantages of both a walking beam suspension whichincorporates air spring(s).

[0005] A further object of the invention is to provide a suspensionsystem which provides a simple way of converting an existing walkingbeam suspension from mechanical springing to air springing.

[0006] With these objects in view the present invention in a firstaspect provides a suspension system for installation between a chassisand dual axles of a vehicle, said suspension system including anequaliser beam pivotally linking said axles together, a trailing armsupport member pivotally attached to a hanger bracket on said chassis, asuspension saddle secured to said trailing arm support to providepivotal support for said equaliser beam and air spring means locatedbetween said chassis and said trailing arm support member.

[0007] Preferably said trailing arm support member is formed from asteel fabrication, a nodular iron casting or a spring steel. In apreferred embodiment said suspension saddle is located below saidtrailing support member and said air spring means is located on theopposing side of said trailing support member. In a practical embodimentthe pivotal attachment of said trailing arm support member to saidhanger bracket includes a releasable offset cam member to provide axlealignment adjustment.

[0008] In a further aspect of the invention there is provided an axleadjustment system for vehicle suspension, said axle adjustment systemincluding a hanger bracket for attachment to the chassis of saidvehicle, a suspension element pivotally attached to said hanger bracket,a pivot pin releasably located within said hanger bracket and having acam element for engagement with said suspension element whereby rotationof said pivot pin causes relative movement between said suspensionelement and said hanger bracket.

[0009] In order that the invention may be clearly understood there shallnow be described by way of a non-limitative examples only preferredconstructions of the invention incorporating the principal features ofthe present invention. The description is with reference to theaccompanying illustrated drawings in which:

[0010]FIG. 1 is a side view of a first embodiment of a vehiclesuspension made in accordance with the invention;

[0011]FIG. 2 is an exploded perspective view of the components of thevehicle suspension shown in FIG. 1;

[0012]FIG. 3 is a cross-sectional view along and in the direction ofarrows 3-3 shown in FIG. 1;

[0013]FIG. 4 is a cross-sectional view along and in the direction ofarrows 4-4 shown in FIG. 1;

[0014]FIG. 5 is a cross-sectional view along and in the direction ofarrows 5-5 shown in FIG. 1;

[0015]FIG. 6 is a side view of a second embodiment of a vehiclesuspension made in accordance with the invention; and

[0016]FIG. 8 is a similar view to that of FIG. 1 of the third embodimentof a vehicle suspension made in accordance with the invention.

[0017] For illustrative purposes, the suspension systems 10,12 in FIGS.1 to 5 and FIG. 6 respectively are shown installed on a tandem axlevehicle. To avoid duplication of description identical referencenumerals will be used for identical components in both embodiments.Since each suspension in the systems is identical to the other, only oneneed be described. The vehicle is the kind having a left side rail framemember 14, a right side rail frame member 16, a forward axle 18 and atrailing axle 20. It will be understood that the suspensions illustratedfor the left side of the vehicle is duplicated with the same kind ofsuspension on the right side of the vehicle.

[0018] An equaliser beam 22 (also known as a walking beam) is formed asa steel or nodular iron casting, a steel or aluminium alloy forging or asteel fabrication. The beam 22 has a pivot centre hole 24 and pivotbushing shells 26. Each bushing shell 26 includes a beam end bush 28which incorporates a compliant rubber element 30 and a steel centre 32that provides for attachment to axles 18,20 through an axle bracket 34.An adjustment method for axle alignment is provided by adjustment shims36. The use of such shims are well known in the art. In the inset shownas “A” in FIG. 2 and in FIG. 5 an alternate beam end bush design isshown that does not incorporate the axle alignment feature of shims 36.This alternative uses an adaptor assembly 38 for attachment to the axles18,20 via axle brackets 34. Assembly 38 includes a support sleeve 40,end plugs 42, threaded fastener 44 and nut 46.

[0019] Located in pivot centre hole 24 is a pivot bush 48 which allowsfor articulation of axles 18,20 and also transfers the vertical forcefrom the vehicle weight and horizontal forces of tractive effort andbraking, through to wheels, tyres and the ground surface. Pivot bush 48usually has a steel inner sleeve 50, compliant rubber element 52 and ansteel outer sleeve 54. The outer sleeve 54 is a press fit in the pivotcentre hole 24 and the inner sleeve 50 extends at each end to accept arespective clamp 56 to locate the pivot bush 48 and beam 22 assembly ina suspension saddle 58. If desired, a lubricatable bronze bushingarrangement could be used to replace the steel and rubber bush 48. Atubular steel cross tube 60 fits into each of the inner sleeves 50 tomaintain alignment of one beam relative to the other. One cross tube 60is used per vehicle.

[0020] Suspension saddle 58 is made as a steel or nodular iron castingor alternatively can be a welded steel fabrication. Lugs 62 are anoptional item for this type of saddle and are used as a location facefor a trailing arm support member 64 in the form of a spring memberwhich fits on to the saddle 58. Two saddles 58 are used per suspension,one each side of the vehicle. Spring member 64 is the main supportmember which acts as a beam member. Spring member 64 can be constructedas a leaf spring assembly with from one to several leaves (as shown). Tohold the leaves together a bolt 65 and nut 67 are used. An eye 66 ofspring member 64 is pivoted at the front end to a frame hanger bracket68 fixed to frame member 14. Spring member 64 is clamped to thesuspension saddle 58 with bolts 70 at approximately a centre positionand has air springs 72 mounted between the centre and the rear of springmember 64. Two spring members 64 are used per suspension, one each sideof the vehicle.

[0021] An adaptor plate 74 is mounted on top of spring member 64 andacts to support the air springs 72. Each air spring 72 has a mountingbracket 76 to allow attachment to frame members 14,16. Bracket 76 issecured to the top plate 77 of air spring 72 with top plate 77 abuttinga respective one of frame members 14,16. In a further embodiment saddle58, spring member 64 and adaptor plate 74 can be manufactured in onepiece. This can be in the form of a steel, aluminium alloy or nodulariron casting, or as a welded steel fabrication. The air springs 72 canbe the industry standard sleeves, rolling lobes or convoluted types. Inthe embodiment shown in FIGS. 1 to 5 two air springs 72 are shown perside. In the embodiment shown in FIG. 6 only two air springs 72 are usedie one each side of the vehicle. The number of air springs 72 used canvary to suit requirements. The air spring(s) 72 of each side areconnected in series to equalise the pressure. Alternately, it ispossible to isolate the air springs on the right side from those on theleft side as an aid to roll stability.

[0022] Hanger bracket 68 is manufactured as a steel or nodular iron oraluminium alloy casting or a steel fabrication. The lower part 78 ofhanger bracket 68 is the upper half of a split cap arrangement, designedto locate, house and restrain a suspension pivot pin 88. Pivot pin 88may be cylindrical and provide no suspension adjustment or be shaped asshown to provide adjustment. Clamps 80 form the lower half of the splitcap arrangement secured by threaded studs 82 which are screwed intohanger bracket 68. Washers 86 and nuts 84 hold clamps 80 in position. Analternative arrangement to this would be the use of a bolt passingthrough clamps 80 to be threaded directly into hanger bracket 68.

[0023] In the embodiment shown pivot pin 88 allows adjustment of axlealignment. A pivot bush 90 is an interference fit in eye 66 of springmember 64. Pivot pin 88 includes a an eccentric element 92 which islocated between support pins 94 and offset therefrom to provide a cammember. Eccentric element 92 is located within pivot bush 90 and canrotate therein. Support pins 94 are clamped by the split cap functionsof lower part 78 of hanger bracket 68 and clamps 80. A square hole 96 isdesigned to accept the square bar of a wrench or turning bar (not shown)so that the eccentric element 92 can be rotated about the diametral axisof support pins 94, inside the split cap housing (when loosened). Thisrotation moves the diametral axis of eccentric element 92 which in turnmoves the spring member 64 of the suspension to provide the adjustment.Square hole 96 may be incorporated into an insert or could alternativelybe any polygonal hole, the criteria being that a key arrangementinserted into the hole can transmit torque to eccentric element so thatit can be rotated, when the nuts 84 of the split cap are loosened. Thisadjustment system is not restricted to this embodiment as it can bereadily incorporated in any spring, trailing arm or other axleattachment arrangement for suspension. Vehicle suspensions benefit fromhaving an alignment adjustment system to allow wheels and tyres to bealigned, relative to the vehicle direction of travel, to provide foroptimum tyre life.

[0024] A longitudinal torque rod or linkage 98 will control driving andbraking torque of the forward driven (or non driven) axle 18. Oneforward longitudinal torque rod 98 would be used per suspension. Afurther longitudinal torque rod or linkage 100 controls driving andbraking torque of the rearmost drive (or non driven) axle 20. Atransverse rod 102 (sometimes referred to as a Panhard rod) controlslateral movement of the axles 18,20 relative to the chassis. Twotransverse rods 102 are used per suspension, one for each of the twoaxles. A spacer and shim pack 104 provides lateral alignment adjustmentof transverse rods 98,100, if required. In an alternate design an“A”-frame arrangement or “V”-rod can be substituted for the twolongitudinal torque rods 98,100 and the two transverse rods 102. Aheight control valve 106 is used to maintain a constant ride height forthe suspension. Normally the suspension will use a single height controlvalve 106 but an alternative may use two valves as an aid to rollstability. Two valves would normally be used, one each side, when theleft and right air springs are isolated from each other. A hydraulicshock absorber (damper) 108 provides hydraulic control of suspensionmovement. The suspension will normally have 4 shock absorbers 108, 110per suspension, ie two per axle (as shown in FIG. 1) but an alternativewould be for two shock absorbers 108 (as shown in FIG. 2) fitted to rearaxle 108 only.

[0025] In FIG. 8 there is shown a further embodiment where the samereference numerals have been used to avoid duplication of description.In this embodiment trailing arm support 64 (FIG. 1) is in the form of asteel fabrication 120. Fabrication 120 is T-shaped in cross-section andhas suspension saddle(s) 126 secured thereto. The horizontal arm offabrication 120 has the air springs 72 secured thereto. Shock absorber108 is coupled to the free end of trailing arm support 120 and to framemember 14.

[0026] The invention can also be used to convert existing suspensions tothe new type of suspension. Examples of suspensions that can beconverted are the following Hendrickson model series: AR series, Rseries, RT/RT2 series, RTE/RTE2 series, RU series, RUE series, U/U2series, UE/UE2 series, RS series, SR series and VS series.

[0027] Whilst there has been described in the foregoing descriptionpreferred constructions of a suspension system incorporating certainfeatures of the present invention, it will be understood by thoseskilled in the technology concerned that many variations ormodifications and details of design or construction may be made withoutdeparting from the essential features of the present invention.

The claims defining the invention are as follows:
 1. A suspension system for installation between a chassis and dual axles of a vehicle, said suspension system including an equaliser beam pivotally linking said axles together, a trailing arm support member pivotally attached to a hanger bracket on said chassis, a suspension saddle secured to said trailing arm support to provide pivotal support for said equaliser beam and air spring means located between said chassis and said trailing arm support member.
 2. The suspension system of claim 1 , wherein said trading arm is formed from a nodular iron casting.
 3. The suspension system of claim 1 , wherein said trailing arm is formed from a steel fabrication.
 4. The suspension system of claim 3 wherein said trailing arm is T-shaped in cross-section.
 5. The suspension system of said claim 3 , wherein said trailing arm is formed from a spring steel.
 6. The suspension system of claim 1 , wherein said suspension system saddle is located below said trailing support member and said air spring means is located on the opposing side of said trailing support member.
 7. The suspension system of claim 1 , wherein the pivotal attachment of said trailing arm support member to said hanger bracket includes a releasable offset cam member to provide axle alignment adjustment.
 8. The suspension system of claim 1 , further including an axle adjustment system, said axle adjustment system having a pivot pin releasably located within said hanger bracket and having a cam element for engagement with said trailing arm support member whereby rotation of said pivot pin causes relative movement between said trailing arm support member and said hanger bracket.
 9. The suspension system of claim 1 , further including a shock absorber linking the trailing end of said equaliser beam to said chassis.
 10. The suspension system of claim 9 , further including an additional shock absorber linking the other end of said equaliser beam to said chassis.
 11. The suspension system of claim 1 , wherein said air spring means includes dual air springs.
 12. The suspension system of claim 1 , further including a shock absorber linking the trailing end of said trailing arm support member to said chassis.
 13. An axle adjustment system for vehicle suspension, said axle adjustment system including a hanger bracket for attachment to the chassis of said vehicle, a suspension element pivotally attached to said hanger bracket, a pivot pin releasably located within said hanger bracket and having a cam element for engagement with said suspension element whereby rotation of said pivot pin causes relative movement between said suspension element and said hanger bracket. 